Vulcanization of rubber with phosphoro triazine sulfides

ABSTRACT

OR Cl, are improved accelerators and vulcanizing agents for the vulcanization of rubber.   AND Z is   IN WHICH Y is   Triazine sulfides of the formula

United States Patent [191 Trivette, Jr. et a1.

[11] 3,867,358 4 1 Feb. 18, 1975 1 VULCANIZATION OF RUBBER WITH PHOSPHORO TRIAZINE SULFIDES [75] Inventors: Chester D. Trivette, Jr.; Otto W.

Maender, both of Akron, Ohio [73] Assignee: Monsanto Company, St. Louis, M0.

122[ Filed: Dec. 3, 1973 121] App]. N0.: 421,126

[52] 11.8. C1. 260/79.5 C, 260/779, 260/79.5 R,

260/775 [51] Int. Cl C086 11/54, C08f 27/06 {58] Field 01 Search 260/79.5 C, 79.5 R, 779, 260/775 [56] References Cited UNITED STATES PATENTS 3,004,005 10/1961 Malz et a1. 260/79.5 R 3,366,598 1/1968 Westlinning et a1 260/45.8 NZ 3,427,292 2/1969 Godfrey et a1 1. 260/779 Primary ExaminerMe1vyn I. Marquis Assistant Examiner-Deborah L. Kyle [5 7] ABSTRACT Triazine sulfides of the formula (S) P(OR) C N N H! 112 N in which Y is 1 (8 P(OR) I or and Z is 1 (S) P(OR) or Cl or C1, are improved accelerators and vulcanizing agents for the vulcanization of rubber.

25 Claims, N0 Drawings VULCANIZATION OF RUBBER WITH PHOSPHORO TRIAZINE SULFIDES BACKGROUND OF THE INVENTION This invention concerns a class of triazine compounds which are useful as vulcanizing and accelerating agents in the vulcanization of rubber. More particularly, it concerns s-triazine sulfides derived from dithiophosphoric acids.

SUMMARY OF THE INVENTION It has been discovered that phosphorothioic acid triazine sulfides are excellent vulcanizing and accelerating agents for the vulcanization of rubber. Rubber compositions containing the sulfides exhibit improved processing safety and fast cure rates and produce strong vulcanizates. According to this invention an improved class of vulcanizing agents and accelerators for rubber are characterized by the formula c I I N in which Y is and Z is (S) 1 (OR) 2 and Z is or both Y and Z are Y and Z are N and a further preferred sub group is when x is 2.

Branched and unb'ranched alkyl radicals are suitable for the practice of the invention with lower alkyl radicals of 1-4 carbon atoms being preferred. Illustrative examples are methyl, ethyl. propyl, isopropyl, butyl, isosbutyl, sec-butyl, tert-butyl, amyl. hexyl, heptyl, octyl and tert-octyl. Illustrative examples of cycloalkyl radicals are cyclopentyl. cyclohexyl, 4- methylcyclohexyl, Z-methylcyclohexyl, and cyclooctyl with cyclohexyl being preferred.

Monocyclic six membered ring amino radicals formed by R and R along with the nitrogen atom is a preferred heterocyclic subclass, however, monocyclic and bicyclic five to nine membered amino radicals are suitable. Illustrative examples of heterocyclic amino radicals are pyrrolidinyl, 2,S-dimethylpyrrolidinyl, piperidino, 4-methylpiperidino, morpholino, thiomorpholino, 2,6-dimethylmorpholino, hexahydro-lH- azepin-l-yl, hexahydro-1(2H)-azocin-l-yl. and azabicyclo(3.2.2)non-3-yl.

Illustrative compounds of this invention are:

2,4-di(0,0-dimethylphosphorotrithioyl)-6-(N,N-

dimethylamino)- l ,3 ,S-triazine 2,4-di(0,0-dimethylphosphorotrithioyl)-6-(N,N-diethylamino )-l ,3,5-triazine 2,4-di(0,0'-dimethylphosphorotrithioyl)-6-(N,N-

diisopropylamino)-1,3,5-triazine 2,4-di(0,0'-dimethylphosphorotrithioyl)-6-(N.N-

dibutylamino) l ,3,5-triazine 2,4-di(0,0'-dimethylphosphorotrithioyl )-6-( N,N-

dibenzylamino )-l ,3 ,S-triazine 2,4-di(0,0'-dimethylphosphorotrithioyl)-6- (piperidino)-l,3,5-triazine 2,4-di((),O'-dimethylphosphorotrithioyl)-6 (2,6dimethylmorpholino)-l ,3,5-triazine 2,4 di(0,0-dimethylphosphorotrithioyl)-6- (hexahydro-lH-azepin-l-yl)-l,3.5-triazine 2 ,4-di(0, 0'-diisopropylpho sphorotrithioyl)-6-(N .N

dimethylamino l ,3 ,S-triazine 2,4-di(0,0'-diisopropylpbosphorotrithioyl)-6-(N,N-

dipro pylamino l ,3 .S-triazine 2,4-di(0,0-diisopropylphosphorotrithioyl)-6-(N,N-

dihexylamino)-l ,3,5-triazine 2,4-di(0,0'-diisopropylphosphorotrithioyl)-6-(N- ethylN'cyclohexylamino)-l,3,5-triazine 2,4-di(0,0-diisopropylphosphorotrithioyl)-6- (pyrrolidinyl-l,3,5triazine 2,4-di(0,0'-diisopropylphosphorotrithioyl)-6-(4- methylpiperidino l ,3,5-triazine 2,4di((l,O-dibcnzylphosphorotrithioyl)-6-(N,N-

dimcthylamino l .3,5-triazine 2.4-di( O,(l'-dibcnzylphosphorotrithioyl )-6-( N ,Ndiethylamino)-l,3.5-triazine 2,4-di(0,0-dibenzylphosphorotrithioyl)-6-(N,N-

diisopropylamino l ,3.5-triazine 2,4-di(0,0'-dibenzylphosphorotrithioyl)-6-(N,N-

dicyclohexylamino)-l,3,5-triazine 2,4-di(0,0'-dibenzylphosphorotrithioyl)-6-(morpholino)-l,3.5-triazine 2,4-di(0,0'-dicyclohcxylpbosphorotrithioyl)-6-(N.N-

dimethylamino)-l,3.5-triazinc 2,4-di(0,0'-dicyclohexylphosphorotrithioyl)-6-(N,N-

dipropylaminoH ,3 ,S-triazine 2,4-di( 0,0'-dicyclohcxylphosphorotrithioyl )-6-( N .N-

dibutylamino l .3.5-triazinc phorotrithioyl compounds are prepared by reacting phosphoryl sulfenyl chloride with 2-mercapto-4,6 diamino-l,3,5-triazine or with 2-mercapto-4-amino-6- chloro-l,3,5-triazine. Alternatively, they are prepared by reacting a salt of dithiophosphoric acid with 2-(4,6- diamino)-l,3,5 triazine sulfenyl chloride or with 2-(4- amino-6-chloro)-l,3,5-triazine sulfenyl chloride.

The 2,4-di(phosphorodithioyl )-6-amino-l ,3,5- triazines are prepared by reacting two moles of a salt of dithiophosphoric acid with 2,4-dichloro-6- amino- 1,3,5-triazine. Examples of suitable 2,4-dichloro-6- amino triazine intermediates are illustrated in .lour. Am. Chem. Soc., 73, pages 2,981 and 2,984. The 2,4- di(Phosphorotrithioyl)-6-amino-1,3,5-triazines of this invention are prepared by reacting a 6-amino-s-triazine-2,4-disulfenyl chloride with an alkali metal salt or amine salt of a dithiophosphoric acid. The reaction takes place under mild conditions and the product recovered and purified by conventional procedures. However, contrary to 'conventional order of addition of reactants, it is preferred in the preparation of the compounds of this invention to add the salt of the dithiophosphoric acid to the sulfenyl chloride. The 6-aminotriazinedisulfenyl chloride is prepared by chlorination of the appropriate 6-amino-dimercapto-triazine, exam ples of which are shown in US. Pat. No. 3,366,598.

The nature of the substituents attached to the triazine ring has a pronounced effect upon accelerator activity. For example, phosphorotrithioyl compounds are more potent accelerators than the corresponding phosphorodithioyl compounds. Compounds with dialkylamino substituents exhibit faster cure rates than the corresponding compounds with heterocyclic amino substituents. Compounds with two amino substituents exhibit faster cure rates than compounds with only one amino substituent. Even the nature of the group attached t the oxygen of the phosphoryl moiety effects the properites of the accelerator in rubber. For example, compounds with a secondary or tertiary carbon attached to the oxygen exhibit greater processing safety than compounds with primary carbon attached to the oxygen of the phosphoryl moiety. Thus, it is apparent that accelerators with any desired combination of properities may be tailored by selection of the proper substituents. The di-(phosphorotrithioyl)-monoamino-triazines are a preferred class of compounds because they possess an excellent balance of properties, namely adequate processing safety, sufficient cure rate and crosslinking efficiency. In addition, vulcanizates containing di(phosphorotrithioyl) triazines exhibit higher moduli than the vulcanizates containing the corresponding di(phosphorodithioyl) triazines which improvement is believed to be the result of the formation of crosslinks in the rubber comprising a bridge consisting of a triazine moiety joined to the rubber molecule through two sulfur atoms attached to two different carbon atoms of the triazine ring. Said mono-sulfidic crosslinks are believed to impart the improved reversion resistance exhibited by the vulcanizates vulcanized using di(phosphorotrithioyl) triazines.

The triazine sulfides of this invention are utilized in the same manner as conventional vulcanizing agents and accelerators, namely by incorporation into the rubber compositions and heating to effect vulcanization. The quantity of triazine compound required varies depending upon the properites desired in the vulcanizate. Generally, the quantity of triazine sulfide is greater when used as a vulcanizing agent that when used as an accelerator in combination with sulfur. Amounts of 0.2-10 parts of triazine sulfide per 100 parts rubber are suitable with amounts of O.53.0 parts per 100 parts rubber being the range normally employed. The triazine sulfides of this invention can be used in any sulfur vulcanizable diene rubber. Natural and synthetic rubbers and mixtures thereof are suitable. Synthetic rubbers include cis-4-polybutadiene, butyl rubber, ethylene-propylene terpolymers, polymers of 1.3- butadiene, polymers of isoproene, copolymers of 1,3- butadiene with other monomers, for example, styrene, acrylonitrile, isobutylene, and methylmethacrylate.

The triazine monoand disulfides are accelerators for the vulcanization of rubber compositions containing sulfur-vulcanizing agents and the disulfides are vulcanizing agents which may be used without other vulcanizing agents being present. Sulfur-vulcanizing agent means elemental sulfur or sulfur containing vulcanizing agent which at cure temperature or below releases sulfur in the form available to cross-link the rubber. Illustrative vulcanizing agents are amine disulfide and polymeric polysulfide, for example, alkyl phenol disulfides and dimorpholinodisulfide. The rubber compositions may contain the usual compounding ingredients, for example, reinforcing pigments such as carbon black or silica, metal oxide activators such as zinc oxide, organic activators such as diphenyl guanidine, stearic acid, antidegradants of the phenolic or amine type, for example, alkylene-bridged cresols, styrenated phenol, sterically-hindered hydroquinones, quinones and N-alkyl- N-phenyl-p-phenylenediamines.

Of course, the triazine sulfides of this invention may be used in combination with conventional accelerators and vulcanizing agents. For certain applications it is sometimes advantageous to employ curative combinations. Examples of conventional materials which may be used in combination with the triazine sulfides of this invention are Z-mereaptobenzothiazole, bis (2- benzothiazolyl) disulfide, N-cyclohexyl-Z-benzothiazolesulfenamide, N-tert-butyl-Z-benzothiazolesulfenamide, N-diisopropyl-Z-benzothiazolesulfenamide,

2-(morpholinothio) be nzothiazole, 2(hexahydro-l I-lazepin-l-yl) benzothiazole, tetramethylthiuram disulfide, tetraethyl thiuram disulfide, bis(0,0- diisopropylthiophosphoryl) disulfide, tetramethyl thiuram monosulfide and zinc 0,0di-n-butylphosphorodithioate.

For the rubber stocks tested and described herein as illustrative of the invention, Mooney scorch times are determined by means of a Mooney plastometer. The time in minutes (2 required for the Mooney reading to rise five points above the minimum viscosity is recorded. Longer times on the Mooney scorch test are desirable because this indicates greater processing safety. Cure characteristics are determined at the designated temperatures by means of the Monsanto Oscillating Disk Rheometer which is described by Decker, Wise and Guerry in Rubber World, December, 1962, page 68. From the rheometer data, the maximum torque, R max., in rheometer units is recorded. The increase in torque is a measure of the degree of vulcanization and is proportional to the cross-link density. The time, t in minutes for a raise of two rheometer units above the minimum reading of the rubber sample, and the time, r required to obtain a torque of 90 percent of the maximum is recorded. The difference, [go t2, is

a measure of the cure rate of the sample. Reversion, a

measure of crosslink scission. is determined by observing the decrease in rheometer torque after maximum torque is achieved. Reversion is recorded in rheometer units and is the difference in rheometer maximum torque and rheometer torque 10 minutes after maximum torque is achieved. Vulcanizates are prepared by press curing at the selected temperature for the time indicated by the rheometer data to obtain optimum cure. The physical properties of the vulcanizates are measured by conventional methods.

DESCRIPTION OF PREFERRED EMBODIMENTS The following illustrate suitable synthesis procedures:

A slurry of cyanuric chloride (92.2g.,0.5 moles) suspended in 200 ml of hot acetone and a solution of morpholine (43.5g,0.5 moles) ol sodium carbonate (35.(\g,0.34 moles) in 275 ml of water are simultaneously added to 300 ml of water with vigorous stirring. The amount of each reactant added is controlled to maintain the pH between 7 and 8 and the temperature of the reaction mixture is controlled between 5C. The addition is completed in 30 minutes. After stirring the mixture 1 hour, a white precipitate is recovered by filtration, washed with water and dried. 2,4-dichloro6- morpholino-1,3,5-triazine m.p. l50l53C is recovered in 75 percent yield.

A slurry of 2,4-dichloro-6morpholino-l,3.5-triazine (823g, 0.35 moles) and thiourea (548g. 0.72 moles) in 500 ml of methanol were stirred 25 minutes until a solution was obtained (monothiuronium salt formed). The solution is refluxed for 2 hours. A precipitate (dithiuronium salt) formed after about I hour. Potassium hydroxide (39.8g,0.7l moles) in lOO ml of water is added in 5 minutes and the mixture is refluxed an additional 30 minutes. The reaction mixture is poured into 1 liter of ice water and the solids recovered by filtration. The product is washed with water and then vacuum dried at 50C. Fifty-seven grams of 2,4- dimercapto--morpholino-1,3,5-triazine, mp. 355-360C. is obtained. Chlorination of the dimercapto compound in an inert solvent gives the disulfcnyl chloride.

Diisopropyldithiophosphate (44g,0.2 mole) is added at 5l0C to a solution of sodium hydroxide (8.0g,0.2 mole) in 300 ml of methanol. 2,4-dichloro-6morpholino-l,3,5-triazine (23.5g.0.l mole) is then added and the reaction mixture refluxed for 3 hours. Sodium chloride byproduct is separated by filtration and methanol is stripped from the filtrate on a rotary evaporator.

A white solid is recovered which is washed with ether and dried. 2,4-di(0,0-diisopropylphosphorodithioyl)- o-morpholino-l,3,5-triazine, 44 grams, m.p. l l6-l 19C is obtained.

A solution containing 0.2 moles ofdiethyldithiophos phate and 0.3 mole of triethylamine in l00 ml of benzene is added in small portions to a stirred solution containing O.l mole of -morpholino-s-triazine-Z,4- disulfenyl chloride in 200 ml of benzene while maintaining the temperature between 2025C. The reaction mixture is stirred for 1 hour at room temperature. The byproduct amine salt is separated by filtration and washed with benzene. The benzene filtrate is washed three times with 300 ml portions of water and then dried over sodium sulfate. The benzene is vacuum stripped in a rotary evaporator at C. to give 45.8 grams of an off-white solid. Recrystallization of the crude product gives essentially pure 2,4-di(0,0'- diethylphosphorotrithioyl)-h-morpholino-l3,5- triazine, m.p. l l l-l 12C.

Substituting 0,0-diisopropyldithiophosphate into the above procedure gives 2,4-di(0,0'- diisopropylphosphorotrithioyl )6-morpholino-l ,3 ,5 triazine. m.p. l36l38C.

A solution containing 0.2 moles of 0,0- diisopropyldithiophosphate and 0.3 mole of triethylaminc in 100 ml of benzene is added in small portions to a stirred solution containing 0.1 mole of 6 diethylaminos-triazine-2,4-disulfenyl chloride in 200 ml of benzene over a period of nine minutes at 2025C. After stirring the mixture for 1 hour at room temperature, the by-product amine salt is separated by filtration. The filtrate is washed with water, dried over sodium sulfate and the benzene is evaporated in a rotary evaporator. A yellow oil is obtained which crystallizes upon standing. The solid is washed with methanol and recovered by filtration to give 2,4-di(0,0'- diisopropylphosphorotrithioyl )-6-dieth vlamino-l ,3 ,5- triazine, m.p. 98C.

The cure characteristics of the phosphoryl triazine sulfides of this invention are demonstrated in the tables below. A natural rubber masterbatch is prepared by mixing parts natural rubber, 45 parts lSAF carbon black, 30 parts zinc oxide, 2.0 parts stearic acid, 5.0 parts softener and 2.0 parts N-l,3-dimethyl-butyl-N- phenyl-p-phenylenediamine antidegradant which masterbatch is used to illustrate the invention. To portions of the masterbatch, quantities of phosphoryl triazine sulfide and sulfur are added and the properties of the vulcanizable compositions and vulcanizates determined.

TABLE l Stock l 2 3 4 5 6 7 Masterbatch l5 7 .0 Sulfur l.0 l.O l 0 L0 2.4-di(0,0'-diethyl- 3.0 l.0 phosphorotrithioyU-d morphnlinol 3 .S-triazine Z.4 cli(0,0'-diisopropyl- 3.0 1.0 phosphorotrithioyl Hi (N.Ndieth vlamino)-L35 triaizine 2.4-ditU,U'-diisoprnpyl- 3.1) ll) phosphorotrithioyl )6- morpholino-l,3,5-triazine 1-[0,0'-diisopropyla. LU

phosphoroirithioyl )4,b-di- (N.N diethylamino)- l 3.5- triazine TABLE l-Continued Stock I 2 3 4 5 6 7 Mooney Scorch at 250F 1 42.0 97.0 103.4 32. s Rhometer Data at 292F 4 48 12] max. 45.8 40.0 37.5 52.2 StressStrain at 292F 6] "I Cure time. minutes 90 120 I 35 (:0 30 15 50071 Moduluspsi 1040 880 880 1120 1470 1120 1100 t. tensi e.ps1 3390 3230 3020 3620 3950 3 Rheometer Data at 328F 840 3710 1. 1. 7.9 12.0 13.8 2.5 3.1 3.1 2.2 R. max 42.9 38.1 38.3 48.1 52.2 48.2 46.5 Reversion 0.5 0.1 0.4 3.3 (1.9 1.8 3.4

The data show that the triazine disulfides of this in- TABLE 111 vention are vuleanizing agents when used alone and that they are delayed-action fast curing accelerators Stock 1 2 3 4 when used with sulfur. The effect of the substitutents 2U Masterbatch 157.0 upon cure eharactenstics is pronounced. For example. Sulfur O 7 0 the presence of a secondary alkyl group on the phos- 2 -l-di(0.0'-diisopropyl- 0:5 1.0 phoric acid moiety enhances the processing safety sigpmsplmlmmhloyllie".

. morpholmo-l.3.5-tr1az1ne nificantly when the triazme disullide is used either as a vulcanizing agent or as an accelerator. (Compare -l S P PY (15 phosphorodlthioyl)-6- Stocks 1 vs 3 and 4 vs 6 When used as an accelerator. the triazinc compound having a dialkylamino substitu- M S h 78 0F tent is a more potent accelerator than the correspondt mlnutes 28.0 64.6 111.2 mg triazme compound having an heterocyclieammo Rheumcm Dum u 292 substituent. (Compare Stocks 5 and 0). An accelera r rim-u 16.5 47.5 x24 N0 cure with two amino substituents in the triazine ring (Stock 0 b d h StressStr-am at 292 F 7) enhances the cure rate ut re uces t 0 processing Cure time m-mums 40 I20 I20 safety of the compos1t1on. 300% modulus, psi 1230 790 1200 Ult. tensile. psi 3680 1980 3670 Rheometer Data at 328F TABLE 11 ao 2 4.5 14.0 15.7 R. max. 45.7 30.1 41.6 Reversion 4.7 l 5 0.2 Stock 1 2 3 4 M t b'tch 157.0

er 40 The vulcanization characteristics of mono-sulfide Sulfur 1.0 1.0 2.4-di(0.0'-diethylphos 3.0 r0 and disulfide triazmes are compared in Table 111. The p p y l-f t monosulfide compound has greater processing safety pmhm'l'lhmzme but the disulfide compound is a more efficient acceler- 2.4-di(Z-henzothiazolyl- 3.0 1.0 ator which cures faster and produces higher modulus 'g f 'p' lg vulcanizates. The disulfide is a vulcanizing agent flLlZl Mooney Scorch a! 2500}: whereas the monosulfide 1S ineffective when used 1, minutes 40.0 41.3 37.1 29.6 alone- Rheometer Data at 292F Although the invention has been illustrated by typical m 28.9 55.9 12.4 16.1 examples, it is not limited thereto. Changes and modifiig'fg'gj n D 570 513 5 50 cations of the examples of the invention herein chosen Cum "mm minulgs 95 35 40 for purposes of disclosure can be made which do not 000; modulus. psi 1340 970 1100 9x0 constitute departure from the spirit and scope of the UL tensile. psi 3490 3310 3320 2910 Rheometer at 328F mVQnnOn' W M 3,8 9 41) The embodiments of the invention 1n which an exclu- R. max. 49.7 43.2 49.0 40.3 55 sive property or privilege is claimed are defined as fol- Reversion 0.6 1.5 3.0 3.7

lows:

l. The process of accelerating the vulcanization of rubber which comprises heating sulfur-vulcanizable diene rubber and sulfur vulcanizing agent with an accelerating amount of a compound of the formula (5) P (CR) 2 in which Y is P (R) 2 or -N and Z is The process of claim 2 in which is 2. The process of claim 3 in which R is isopropyl. The process of claim 1 in which Y is and Z is 6. The process of claim 5 in which x is 2.

7. The process of claim 6 in which R and R are lower alkyl.

8. The process of claim 7 in which R is isopropyl.

9. The process of claim 6 in which is an heterocyclic radical.

11). The process of claim 9 in which R is isopropyl. 11. The process of claim 10 in which is morpholino.

12. The process of vulcanizing rubber which comprises heating sulfur vulcanizable diene rubber with a vulcanizing amount of a compound of the formula S P (0R) 2 in which Y is and Z is or Cl in which each R independent is alkyl of l-8 carbon atoms, cycloalkyl of 5-8 carbon atoms, benzyl. phenyl or tolyl, and R and R independently are hydrogen, alkyl of 1-8 carbon atoms, cycloalkyl 015-8 carbon atoms, benzyl, phenyl or tolyl or R and R. to-

gether with the nitrogen atom from a heterocycle of 4-8 carbon atoms which heterocycle may be interrupted by oxygen or sulfur.

13. The process of claim 12 in which Z is 14. The process of claim 13 in which R is isopropyl.

15. The process of claim 14 in which R and R are lower alkyl.

16. The process of claim 15 in which R and R are ethyl.

17. The process of claim 14 in which is an heterocyclic radical.

18. The process of claim 17 in which is morpholino.

19. A vulcanizable composition comprising diene rubber and a vulcanizing amount ofa compound of the formula or Cl in which each R independently is alkyl of 1-8 carbon atoms, cycloalkyl of 5-8 carbon atoms, benzyl, phenyl or tolyl, and R, and R independently are hydrogen, alkyl of l-8 carbon atoms, cycloalkyl of 5-8 carbon atoms, benzyl, phenyl or tolyl or R and R together with the nitrogen atom from a hetcrocyclc of 4-8 carbon atoms which heterocycle may be interrupted by oxygen or sulfur.

20. The composition of claim 19 in which Z is 21. The composition of claim 20 in which R is isopro- Py 22. The composition of claim 21 in which R and R are lower alkyl.

23. The composition of claim 22 in which R and R are ethyl.

24. The composition of claim 21 in which is an heterocyclic radical.

25. The composition of claim 24 in which is morpholino. 

1. THE PROCESS OF ACCELERATING THE VULCANIZATION OF RUBBER WHICH COMPRISES HEATING SULFUR-VULCANIZABLE DIENE RUBBER AND SULFUR VULCANIZING AGENT WITH AN ACCELERATING AMOUNT OF A COMPOUND OF THE FORMULA
 2. The process of claim 1 in which Y and Z are
 3. The process of claim 2 in which x is
 2. 4. The process of claim 3 in which R is isopropyl.
 5. The process of claim 1 in which Y is
 6. The process of claim 5 in which x is
 2. 7. The process of claim 6 in which R1 and R2 are lower alkyl.
 8. The process of claim 7 in which R is isopropyl.
 9. The process of claim 6 in which
 10. The process of claim 9 in which R is isopropyl.
 11. The process of claim 10 in which
 12. The process of vulcanizing rubber which comprises heating sulfur vulcanizable diene rubber with a vulcanizing amount of a compound of the formula
 13. The process of claim 12 in which Z is
 14. The process of claim 13 in which R is isopropyl.
 15. The process of claim 14 in which R1 and R2 are lower alkyl.
 16. The process of claim 15 in which R1 and R2 are ethyl.
 17. The process of claim 14 in which
 18. The process of claim 17 in which
 19. A vulcanizable composition comprising diene rubber and a vulcanizing amount of a compound of the formula
 20. The composition of claim 19 in which Z is
 21. The composition of claim 20 in which R is isopropyl.
 22. The composition of claim 21 in which R1 and R2 are lower alkyl.
 23. The composition of claim 22 in which R1 and R2 are ethyl.
 24. The composition of claim 21 in which
 25. The composition of claim 24 in which 